1. Field of the Invention
The field of this invention relates to blends of crystalline copolyamides obtained from hexamethylene diamine (HMDA) and mixtures of compounds of terephthalic acid (TA) and isophthalic acid (IA) in combination with glass fiber, graphite fiber or mixtures thereof.
2. Background
Filled compositions of crystalline copolyamides from hexamethylene diamine and mixtures of compouds of terephthalic acid and isophthalic acid in which the TA content exceeds 70 mole percent of the acid moieties have not been disclosed in the prior art. In particular, blends in which these copolyamides are combined with glass fibers, graphite fibers or mixtures thereof and have heat deflection temperatures in excess of about 240.degree. C. are unknown. In fact, U.S. Pat. No. 3,382,216 teaches that the preparation of polyhexamethylene terephthalamide cannot be effected through melt condensation processes.
U.S. Pat. No. 4,118,364 (1978) discloses polyamides of isophthalic acid and hexamethylene diamine filled with reinforcing materials such as glass fibers.
U.S. Pat. No. 3,941,755 (1976) discloses a copolyamide for fiber formation prepared with hexamethylene diamine which has a molar ratio of TA to IA of between about 60:40 and 80:20. However, this patent does not disclose the use of fillers. There is no suggestion that the compositions of the instant invention would have such unexpectedly high heat deflection temperatures. Other U.S. Pat. Nos. which similarly disclose a fiber forming copolyamide with a TA to IA ratio of up to 80:20 include 4,238,608 (1980); 4,113,708 (1978); and 4,022,756 (1977). None of these patents suggests the use of a filler. In fact, all of these patents teach that a high TA copolymer is not useful due to "phase-out" which can occur at TA levels greater than 60 mole percent (see column 2, lines 24-35 of U.S. Pat. No. 3,941,755). Additionally, there is no suggestion that a material with a heat deflection temperature greater than about 240.degree. C. can be obtained by using certain fillers.
Other patents which might be of interest include U.S. Pat. No. 3,294,758, which discloses that compositions containing greater than 30 percent hexamethylene diamine are brittle. U.S. Pat. Nos. 3,825,516, 3,962,400, 3,941,755, 3,627,736, 3,692,749, and 3,382,216 disclose amorphous polyamides.
It is clear from a review of these references that the filled crystalline polyphthalamides manufactured from HMDA and mixtures of TA and IA wherein the TA content exceeds 70 percent of the total acid moieties, having heat deflection temperatures of about 240.degree. C. to about 305.degree. C., are unknown to the prior art. As used herein, a "crystalline" polymer is defined to be a polymer having a measurable, well-defined melting temperature.